Maggot Gut Content Studies

Identifying, and/or individualizing, the source of the gut content of forensically important insects could potentially identify a victim from a maggot left behind when a corpse was moved. A blood-feeding insect at a scene could connect a suspect to that scene if it were found to have fed on the suspect. Campobasso et al. (2005) reviewed these and other potential applications of this analysis.

The variety of taxa represented in gut content literature is limited. Mostly blowfly species have been examined (Linville et al. 2004; Linville and Wells 2002; Zehner et al. 2004b). The flesh flies and the muscids have received little attention in this area of research (Wells et al. 2001b). The remainder of the literature deals with mosquitoes (Culicidae) (Kreike and Kampfer 1999; Mukabana et al. 2002), lice (Pediculidae) (Replogle et al. 1994; Lord et al. 1998; Mumcuoglu et al. 2004), and a sap beetle (DiZinno et al. 2002). Future work in this area should incorporate a wider variety of species.

Short tandem repeat (STR) analysis is the standard for the determination of human nuclear DNA profiles. Countries around the world have adopted a somewhat overlapping set of standard STR loci for human identity testing (Butler 2005). Recent gut content studies have used STR loci as markers (Schiro 2001; Linville et al. 2004; Mumcuoglu et al. 2004; Zehner et al. 2004a).

Human forensic geneticists are constantly developing methods that are more discriminating and/or applicable to tissue samples that were previously unsuitable for analysis. Almost certainly these will be increasingly used for forensic insect gut content analysis. For example, Y-STR analysis is a new tool in forensic laboratories (Butler 2003). It has not yet become standard practice for most publicly-funded laboratories, but it will become more widely available in the future. Y-STR loci are so named because they reside on the Y chromosome, so they are useful for detecting human male DNA in a sample. One obvious application of this technology is the detection of semen on the remains of a victim of sexual assault-homicide. Limited work has been done to detect semen in the gut content of maggots (Clery 2001). This combination of STR profiling and gut content analysis could prove to be extremely useful in an investigation. Researchers working on gut content analyses should incorporate such new developments into their studies.

As pointed out by Campobasso et al. (2005), feeding stages usually are needed for the successful isolation of host DNA from the alimentary tract of the larvae. However, Carvalho et al (2005) reported fragments of 197 basepairs (bp) and 87 bp of host sheep DNA (satellite I region) in all stages of immatures, including 2-day-old pupae of Calliphora dubia.

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